There are three types of patent holders:
1. They constantly develop and update their stuff, like ARM. ARM doesn't manufacture processors, but it does constantly develop new architectures.
2. They sit on bland, obscure patents, such as patents dating back to the late 1990's or early 2000's, and are only widely known when they file lawsuit. RAMBUS would be a great example.
3. They use patents to obstruct their competitors and to gain market advantage over them. Pretty much every tech company falls under this category, including Apple.